黑碳团簇气溶胶混合生长的红外吸收特性及长波辐射效应

黑碳气溶胶是当前气溶胶辐射强迫评估中最不确定的因子.本文通过构建黑碳的微物理模型,分别模拟了新鲜状态的黑碳气溶胶和混合生长(老化)后被硫酸盐包裹的黑碳气溶胶,利用叠加T矩阵方法计算获得了具有团簇形态和多成分混合的黑碳气溶胶红外吸收特性,通过大气辐射传输模型模拟了黑碳气溶胶的长波辐射强迫,分析了典型理化参数的敏感性.发现黑碳混合生长可以显著增强其大气层顶的长波辐射强迫,最高可达3倍.而且,包裹黑碳的硫酸盐半径越大,将明显增强大气层顶的黑碳长波辐射强迫.这些发现将有助于降低黑碳气溶胶气候效应评估的不确定性.

Effect of aggregated black carbon aging on infrared absorption and longwave radiative forcing

Black carbon aerosols affect the shortwave and longwave radiation in climate in a strong yet uncertain way. In aging process, black carbon particles coated by co-emitted aerosols tend to reduce the shortwave radiative forcing of freshly emitted black carbon at the top of atmosphere (TOA), however, this effect is still unclear in the longwave range. Here in this work, we investigate the effect of black carbon aging on longwave radiative forcing. The freshly emitted black carbon aerosols are simulated to be fractal aggregates consisting of hundreds of small spherical primary particles, and these aggregated black carbon aerosols tend to be fully coated by the large sulfate particles after aging. The optical properties of these freshly emitted and internally mixed black carbon aerosols are simulated using the numerically exact superposition T-matrix method, and their longwave radiative forcings are calculated by the radiative transfer equation solver. The results indicate that the black carbon longwave radiative forcing at TOA is remarkably amplified (up to 3) by coating the large sulfate particles, while the black carbon shortwave radiative forcings decrease during their aging. Moreover, the thicker sulfate coatings tend to increase the longwave radiative forcings of black carbon aerosols at TOA. These findings should improve our understanding of the effect of black carbon aging on their longwave radiative forcings and provide guidance for assessing the climate change.